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so the ...40 is an input shut and not a drive gear so what is ....39? GDS in Florida is sending quotes now thank you

They both are input shafts just for different pilot bearing sizes. If you have adobe reader google fso 6406a parts diagram and a link to a pdf will come up, that is where you will find the parts diagram and numbers.

Glad to see that a few of you are willing to carry the ball for a while. Been having some med issues and trying to heal up to get back in the shop. Still have a few more rounds to go. Injuries from Viet Nam are starting to take their toll on an aging body.

The comments posted about the Fuller bearing retainer and the 38 tooth yoke are correct. In fact, the bearing retainer must be shimmed in order to set the proper preload on the bearing. The yoke is a straight forward torque issue.

T-case Adapter
I have mulled over various ways to accomplish this. The easiest and best way would be to make a bearing retainer with a flat area to bolt to the existing bearing mount with a larger outer ring that is drilled to mate to the GM or Dodge transfer case adapter housing. The bearing retainer is a straight cut to accept the bearing race. The GM adapter is clocked slightly differently than the Dodge adapter. The 38 tooth yoke could be machined down and drilled for a four bolt pattern with a pilot to receive the mating shaft. The mating shaft could be made in two pieces.
1) Machine a round metal piece with pilot to make with the portion mating to the yoke.
2) Use the NV5600 shaft stub and machine it round to .XXXX dim
3) Machine apilot (F orM) to mate with the yoke. Bore the fab'd round piece for a press fit with the NV5600 shaft. Length would have to be predeterined to fit the T-case and fit properly when assembled
4) Weld the round piece to the NV5600 shaft.

Ideally, it would be nice to be able to produce both pieces from blank stock, broach the splines and then machine to fit. This could easily be produced in XXX country for $60.00 or so The bearing retainer adapter about $50. The GM and Dodge T-case adapters are $25.00 or less all day on Ebay. Retail would be about $450.00. McaFab is selling his fo $1,900

The market for a "factory" kit is huge--all class 5-6 trucks have to have divorced T-cases and in some cases, cut & stack the frames. The Fuller trannies are the most simple trannys and in relative terms compared to light duty trannies, BULLET PROOF. With over 56,000 hits on this thread, there is a huge following looking for the final solution.

Perhaps in the near future my cicumstance will get better and can continue the project. Meanwhile, I'm starting the 3rd year with the Fuller and no isuues to date--ever thankful that I ventured into the unknown.

Good luck to all and continue thinking outside the box.

Paul--chansey was my Dalmation and now gone at age 14.

Bullet proof is not a word the light truck makers like to hear. I feel the #1 reason that light truck diesels have never had a Fuller behind them is they can't sell parts as much. True dependability is a swear word to profit. If I had known what I know now I would have put a Cummins in 3yrs ago instead of spending $3,000 repairing the PWRSRTK. The girls and I are looking forward to shifting gears on the FSO behind the school bus Cummins in the F250. still trying to figure out which way to go. ,,..buy or build an FSO. In 1 truck parts site there were 83 FS6406A's for sale...and only 7 FSO's(all well over $2,000.) An intelligent rebuilder would build an FSO instead of an FS... because the market is there... just look at all the light truck and 4x4 forums. I would buy an FSO in a flash at $1,500-1,700.

Even though I have no intention of doing this swap in the near future I am still following this thread closely, I have a dream build in mind and this transmission swap would definitely be a part of it.

I have one question, My truck is only pulling or hauling a small portion of the time, other than that it runs unloaded on the highway. If a person had an engine putting out around 7-800 lb. ft. pounds of torque without running it to death, and was running unloaded, is there a 7 speed transmission that has a double overdrive? Something that when running light on the highway you could drop your engine RPM back to 16-1800 RPM in 7th, then when you loaded up you go run in 6th at around 18-2200 RPM depending on your rear gears. I would think if your engine was set up like a work engine and made most of its power between 16-2200 RPM then this would be a good way to save fuel.

I concur with Chansey If you want a double overdrive you will end up with either an aftermarket product like Advanced Adapter or a Brownie. Both would require additional engineering to install. I feel any thought of the Spicer is a bad move. The internet is rife with 7speed Spicers taking a crap. I am sure there would be an unsynchronized Fuller out there that would have the exra gearing, but you may take a hit with the extra weight. You may be able to find an after market overdrive that will bolt onto the Fuller, but the cost may turn you off.
The FSO8406A is used in a lot of big trucks (including Kenworths and Peterbilts) where the weight is a lesser factor and a lot of running is empty. The overdrive is after all an option to use or not use. In O/D the engine runs at a lower RPM but It may have power problems in winds and loaded. In that type of trip it may be better to stay out of O/D with the engine running in the high rev area of the power curve.

We have a Peterbilt that has a 13 speed behind a 3406 cat and that truck goes so fast that we run in 12th at 1600 at 60 mph and in 13th about 70 mph not sure if its a double overdrive or not or rear end gearing but its fast. too bad the transmission weighs half a ton or it would be in place of the 6 speed i just put in

Ok so if I'm reading the above correctly adding an aux overdrive would allow you to add a certain percentage of speed to each gear. Kind of like a splitter but you adding instead of taking away correct??

Also another question if anyone can answer this. I'm sure the 6406 could probably hold 500hp from a cummins without much problem but how many rpms can it handle? I plan on putting a gsk 5000k on my truck. Now im sure I will very rarely be hitting 5. Maybe 4000s sometimes, but when i do I'd like to know it'll handle the rpms. I don't know a whole lot about transmissions but I would think the higher the rpm the better balanced everything needs to be. And these trannys were probably built with intentions of never exceeding 3000.

Suppose it's about time I got started on the final leg of the Fuller Conversion--making the 4 X 4 T/C adapter to attached the NVG241 to the Fuller FO-8406ASX.

Spent over 40 hrs trying to find companies willing to forge/cast/fab parts needed to make the adapter and shaft. Only one company is willing to work with me--KOVAK--thanks Eric !!!.

I picked-up another NV5600 T/C adapter/support mount for $20.00. Took it to D & R Machine to fab an adaptor plate to join the stock Fuller bearing retainer and the stock NV5600 T/C adapter/support mount for mock-up and dimensioning. After that is completed I will use AutoCad to draw a full dim drawing. I plan on utilizing a single shaft, 38 tooth female (involute) X 29 tooth male spline (T/C).

There will be a few options on how to fab the adapter;

1) a single cast/forged unit with bearing retainer, shaft seal and 6 bolt T/C pattern as a single unit

2) use the Fuller brake adapter and fab a coupler plate to the NV5600 adapter

This week I have already had 5 calls inquiring about availabilty of the adapter. Cost is always a major consideration so I plan on keeping this at a rock bottom price. Cost is also based on a production run of XX units at a time.

Without any committments, I would like to know how many of you would be interested in an adapter.

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